There once was a post here on how to compare images to possibly detect if some images were IDENTICAL to another image to prevent users from uploading an image that is already on file. I don't remember the title of it and I remember someone saying it's not 100% accurate but it's more than accurate enough for a message board.

My question is, is there a way to compare just, well, the CODE of images to each other? Or like the image comparison stuff?

It's hard to explain but to compare a new uploaded image to ALL uploaded images (a few thousand) isn't exactly possible so I was wondering

1) How do we compare images to each other?
2) Is it like a hex code or such where I can save the string of chars to a database and just compare that way instead of re-analyzing each image?

Thanks for your help!

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